This disclosure relates generally to equipment utilized and operations performed in conjunction with a subterranean well and, in an example described below, more particularly provides for maximizing hydrocarbon production while controlling phase behavior or precipitation of reservoir impairing liquids or solids.
Many hydrocarbon reservoirs contain substances which are in solution with the hydrocarbon fluids, be they gas or liquid, or are in an innocuous state such that they can flow freely through the reservoir geologic formation with the hydrocarbon fluids. Most exploitation schemes of hydrocarbon reservoirs involve drilling a well into the reservoir rock, and reducing the pressure in the well to induce flow of the reservoir fluids into the wellbore, so that they can be lifted to the surface. This reduction in pressure in the wellbore permeates into the reservoir itself, creating a pressure gradient deep into the reservoir.
With some fluids, particularly gases, the reduction in pressure is accompanied by a reduction in temperature of the fluids due to isentropic expansion. Unfortunately, this change in pressure and temperature in the reservoir and wellbore can induce physical phase or chemical changes in the aforementioned substances such that these substances precipitate, condense or sublimate in the reservoir pore spaces, natural fractures, induced fractures in the near wellbore region of the reservoir, and in the wellbore itself.
Such precipitation, condensation or sublimation can impair the ability of the hydrocarbon reservoir fluids to flow through the reservoir and into the wellbore, and can cause plugging of the rock and the conduits in the wellbore. Examples of these substances are water condensate, hydrocarbon condensate (in gas-condensate wells), waxes, paraffins, asphaltenes, elemental sulfur, salts and scales. The impact of this problem is greatly accentuated if the reservoir rock formation is particularly “tight”, or characterized by low permeability.
Therefore, it would be advantageous to control the downhole flowing conditions of pressure and temperature using intelligent well technology, that is, sensing and/or flow control, to prevent or minimize the precipitation, condensation or sublimation of these substances, thus ensuring optimum hydrocarbon production rates from the well and maximizing ultimate hydrocarbon recovery from the reservoir. This control may involve human decision making, or may be autonomous.